Dyson not honouring guarantee

I bought a new Cleaner Head for my Dyson in May last year which stopped working in December. It’s under the 1 year guarantee so should be replaced by Dyson, however they don’t have any in stock. They offered a free repair instead. Dyson took it away and it came back unrepaired. They apologised, took it again and it came back again, unrepaired. Except this time they forgot to return the red clip that holds the Cleaner Head on, so now the Dyson is unusable! Support person on the phone said they can’t repair it as they don’t have the Cleaner Head nor the red clip in stock. I emailed support instead and they offered 25% off a new Dyson, but I explained I just want my Cleaner Head replaced under warranty. It’s apparently been escalated twice but I still haven’t had anyone respond with an actual solution and just feel stuck. What can I do at this point? Phone support say they’re escalating it, email support responded to me yesterday to say my issue had been resolved when it hadn’t! I feel like they are deliberately sending me round in circles to get rid of me.